how can i get fragcoord in file shader.frag for sfml shader in csharp

In your shader.frag file, you can get the gl_FragCoord variable using the following code snippet:

#version 120

uniform sampler2D texture;

void main()
{
    vec2 fragCoord = gl_FragCoord.xy;
    
    // Use fragCoord for further calculations
}
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In your C# code where you set the shader for your SFML object, you can load this shader.frag file and set it as the fragment shader for your SFML shader.